Introduction – Monitoring and Maintenance
Michigan Vascular Access, PC follows most patients in a “case management“ model, meaning that patients are encouraged to return with their problems. Knowledge of the patient’s history, previous examinations and procedures, and x-rays in the file help guide a focused examination and problem solving session. Ultrasound is almost always helpful. Frequently, cannulation problems may be due to an incomplete understanding of the patient’s individual access. If so, feedback to the unit, with or without an ultrasound-guided digital photo diagram may solve the problem (see “Ultrasound-assisted digital photo diagrams to guide cannulation” in section above). If an endovascular procedure or an actual operation is advisable, they can be arranged at the earliest or most convenient moment.
In the initial meeting with a new patient with an access complication or failed access (second opinion, or transfer of service), a review of the patient’s access history (including previous procedures) is coupled with a focused physical examination and ultrasound evaluation. Recommendations may include an ultrasound-assisted digital photo diagram, an endovascular evaluation and procedure, operative revision, referral to a more suitable practitioner, or sometimes return to the original surgeon as the best person to manage a complicated problem.
Endovascular (minimally invasive) Evaluation and Correction of Vascular Abnormalities Complicating Dialysis Accesses
Shunts (grafts and fistulas) are all tubes that “shunt” blood directly from the artery to a vein bypassing the normal capillary circulation in the tissues, a situation which normally does not exist in the human body. In order for this abnormal state to be tolerated by the patient and be useful for dialysis, certain conditions must exist: (1) there must be enough blood running in the shunt to allow dialysis (over 600 cc/min), (2) the blood supply in the extremity must be enough to supply the shunt, and still provide enough blood to the forearm and hand, and (3) the amount of extra blood flow required by the shunt must not put an unacceptable strain on the heart. There must be a balance of flow in the shunt.
If an abnormality in a dialysis access is detected or suspected (poor flows and clearances, elevated pressures, cannulation problems, bleeding, or arm swelling – see the “Warning signs” handout), the patient may be advised to have a shuntogram for diagnosis or treatment. The access is punctured with a needle, a tube (sheath) is placed and all interventions are done through the sheath. The circuit can be examined from the arterial inflow, through the shunt, and through the veins all the way back to the heart by injecting contrast. Measurements can be made, narrowings can be stretched, clot can be removed, and stents can be placed, with the goal to save or improve the dialysis access in the least disruptive way possible. These “tune-ups” are normally done as an outpatient.
Operative Revision of Fistulas and Grafts
When a dialysis access is damaged, dysfunctional, or deteriorating, but still has value, a revision may be recommended to restore or save the access. These procedures require incisions. Replacement of a damaged section, removal of an aneurysm, branch ligation, flow reduction and so on – many procedures are offered as needed. Every effort is made to provide a solution that does not require placement of a temporary catheter, but sometimes this is necessary. Frequently an endovascular component (see above) is included with the open procedure.
Central Stenosis – Arm and Facial Swelling
The reason that there is such a concern about dialysis catheters, and a push to get them out, is that they can eventually damage the central veins and interfere with blood returning to the heart. When that happens, and the blood backs up into the tissues, a number of problems can occur, including the very noticeable and uncomfortable arm, breast and facial swelling. Solutions include removal of the dialysis catheter, either for good or by replacing it elsewhere, stretching the damaged veins (see “Endovascular evaluation..” above), placing a stent, performing an operation to reduce flow in the shunt (see below”), or ligation of the access.
Dr. Webb has extensive experience managing central stenosis, maintains a registry with over 220 patients managed with central stents, and has presented his findings at several national meetings. He works closely with an interventional radiologist colleague, Dr. Paul Arpasi, in managing these problems (see images)
When the tissues of the forearm and hand do not receive enough blood, a series of complications can be seen: tingling of the finger tips, intermittent “falling asleep” of the fingers or hand, a sensation of coldness, a change in the sense of touch, numbness, intermittent or constant pain, or non-healing injuries. Most dialysis patients have conditions that predispose them to poor circulation (diabetes, peripheral arterial disease, history of smoking, lupus, and so on), so this problem is very common. The management can be as simple as keeping the hand warm, taking low dose aspirin, and quitting smoking, or it can involve a number of procedures depending on the patients exact circumstances (see images and the “Digital Ischemia” handout)
High Flow Fistulas
Fistulas are veins attached to arteries and expected to grow big enough to be usable. Occasionally they grow too big, and come to have enough flow to strain the heart or deny enough blood to the hand. In some cases the abnormally high flow is measured by especially equipped dialysis machines, and in others a cardiologist may detect it while investigating heart failure. In my practice direct measurements of access flows during a shuntogram are done as indicated when we are suspicious that high flows exist. If the high flows are inconsequential, they can be watched. If associated problems exist, the management usually includes inflow reduction by banding, or by replacing the inflow segment of the access (proximalization or distalization – see images)
Again, occasionally fistulas grow too big, and cause concern. People become worried about rupture of the fistula and bleeding, or are concerned about the appearance. In general, most aneurysmal changes of fistulas are not worrisome unless certain conditions exist: access pulsatility (pounding instead of vibrating), slow flows, rapid growth, local tenderness, or skin thinning/compromise. Reassurance may be all some patients need to hear. An outflow stenosis causing too much back pressure, pulsatility and low flows may need to be dilated. Some aneurysms require an operation: The aneurysm so big that you cannot wear a long sleeve shirt or bang it on the door jamb every time you come in the door may need to be reduced in size. Aneurysms with skin damage, bleeding, rapid growth, or clot inside may require an urgent operation (see images).
Pseudoaneurysms are not accesses which have grown, but rather ruptures in the access that have been contained under the skin, and have a very thin wall. These can be watched carefully in selected cases (in fistulas), but are prone to collect clot, get infected, and go on to rupture. Generally these require surgery (see diagram and images)
Fistulas theoretically can last a lifetime but frequently don’t. Grafts are generally good for three to five years. If the central portion of a fistula becomes unusable, but the ends are still good, or if a graft has become worn out, early cannulation grafts can be used to repair or totally replace the access with another that can be used the very next day, avoiding a catheter. Dr. Webb has extensive experience with early cannulation grafts (Vectra, Flixene, and Acuseal grafts), and has presented that experience at two national meetings (see images).